Purification process



D. A. HIGH PURIFICATION PROCESS Flled Oct 26, 1950 INVENTOR.

DONALD A. HIGH BY ATTORNEY M d.

N GENO In 12 ven atented Dec. 1, 1953 Donald. A; High;. Dayton-, ,Ohio}. assignorzto Mona santo Chemical Company, St. IrouisrMo'g a cors poration of Delaware ApplicationDctobenZG, 1950,:SeriaLNo. [132.30%

4 'CIaimSJ: (Cl. 23-13-149 This; invention relates. to a purifitifiibnmrocesss which. has. particular. utility; for. compositions: containing principally nitrogen andaphosphoruss inchemically combinediorm.

Condensation products of .ammonia.with,phos-.- phorusoxychloride havesbeen described in whichlow percentages of nitrogen. are obtained relativetothe-phosphorus content.) Becauseeofwthe. re-v uirement for nitrogenephosphorus... compounds,

in .fiameproofing treatments an-improvediiorm of relatively higher... nitrogenicontentahas been. prepared. Copending. application Serial No. 169,- 513, filed vJune 21,11950, whichis. assigned .to the same. assignee as. is the. presentcase, describes compositions containing nitrogen and phosphorus which are insoluble in liquid ammonia. Such compounds are prepared .by reacting phosphorus oxychloride with ammonia in aninert .solvent at a temperature below 109 "CI to 'produce'a primary reaction product mixed with by-product ammoniumchloride.- Such reaction mixture is then heated to a temperature ofat least- IOO CL, but below 150-'CI, whereupon it is found; that th'eini-L- tiall'y formed product-ischanged from an-vam monia-soluble form to onewhich is 'substantially' insoluble in liquid anhydrousammonia. According tosthe aforesaid pending application,.the P1 11. ification of--such condensationiproduct to remove ammonium chloride .and'other impurities maygbe carried out by extraction with liquid ammonia? It has now been found that the liquid ammoniaextraction of such nitrogen-phosphorus condensation products may be improved by removing the solvent ammonia containing the ammonium I chloride from the charge in the extractor by displacement with air or an inert gas such as nitrogen at the end of the extraction period. The extraction may be carried out in a pressure vessel provided with a filter unit, or in a suitably arranged filter press. It has been found that the present method results in a great improvement over the direct vaporization of the solvent itself. The advantage of the present method apparently results from the fact that vaporization of ammonia is substantially prevented, a lowering of the solvent ammonia temperature is mitigated so that the high solvent power of the ammonia is retained during the extraction. The improvement resulting from the displacement of ammonia by means of an inert gas is readily seen in the example below, iIlIWhiCh the charge and ammonia ratio are substantially equivalent:

Ammonia expansion Nitrogen displacement Crude charge Wt. percent NILCl (orig) Wt. percent NH Ol (final) The. inert:gasswhicli;isgemployed ito blow th'e s ammoniaofrfomctherextraction:massv may be;any"" inert .gasiwhichlis mot reactive with ammonia: Airimayalsocbe employed in theform ofcom': pressed airs... Itiisalso an'advantage of the .present'process that the. mass of nitrogen-spires phorusrcontaining condensation product .is obs tained atsub'stanti'ally room temperature so that thenmaterialimay more readily be handled. For example, .it' has been found that the vaporization: of ammonia fromma typical extraction charge of the above described material chills the product from 35 C. to below 0 0., whereas the displacement of the ammonia by nitrogen leaves the temperature of the mass substantially unchanged at.

up jfor...subsequent ih'andling after :tlie. extraction operatiom... Shelidiffi'culties are avoided by, the. present .methodlimwhiohi th'e liquiiammonia is displaced.lon1;bldwn..out.ofi. the..product by means of. faninertjgas under .pressura MyiH-inventionmis.furtherillustrated .bymeans ofitheaccompanyingpdfaw-ing exemplified. in. an embodiment-. of.'IT'the...inyention.- The process is illustrated by means of a diagrammatic flow sheet of the process in which only the essential elements are shown.

In the drawing, N indicates a reactor or autoclave into which ammonia is charged from pipe ll, phosphorus oxychloride is charged from pipe l2 and a solvent such as as hexane is charged from pipe I3. The reaction is so conducted as to yield an ammonia-insoluble reaction product of the phosphorus oxychloride and ammonia, after which the major portion of the solvent may be remmoved from vent 14. In order to aid in the removal of solvent the reactor may be heated by means of temperature control jacket I5.

The crude product leaves the reactor by means of pipe 20 and is then passed to drier 2!, from which further solvent may be removed by means of line 22.

In order to remove by-product ammonium chloride from the phosphorus-nitrogen condensation product, the dry material may be transferred by line 23 to an extractor or filter 30. The extractor may be a suitable vessel provided with filter element 3| for the retention of the insoluble condensation product. The extractor is also provided with lines 35 and 36 for the introduction of nitrogen under pressure and of liquid ammonia, although a common entry may be employed. The vessel is also provided with a drawoff 34 for the removal of ammonia containin the dissolved by-product ammonium chloride.

In the operation of the extraction process the crude phosphorus-nitrogen compound is charged to the extractor, after which sufficient liquid ammonia for the solution of the contained ammonium chloride is added. The mixture may be agitated, if desired, or may be extracted simply by passage of liquid ammonia. through the mass of crude material. The solvent ammonia, together with the dissolved ammonium chloride, is then released from the vessel. However, in removing the ammonia from the system, it is essential that the nitrogen or other inert gas be introduced under pressure into the extractor to displace the ammonia. It is found that when this step is carried out there is a reduction in the coolride"'from admixture therewith of condensation products of phosphorus oxychloride and anhydrous ammonia obtained by heating the said reactants to a temperature of at least 100 C. but below 150 0., adding liquid anhydrous ammonia to said reaction mixture to dissolve ammonium chloride therefrom, and thereafter applying niing effect which would otherwise result by the va porization of the liquid ammonia. Thus, the solid material remaining in the filter element or extractor is obtained in substantially pure form and at room temperature.

In order to simplify the description of the invention, the required valves, measuring and control devices have been omitted. The proper placement of such means and devices will be understood by one skilled in the art in view of the foregoing descriptions.

What is claimed is:

1. In the process of extracting ammonium chloride from a mixture with condensation products of phosphorus oxychloride and ammonia obtained by heating the said reactants to a temperature of at least 100 C. but below 150 0., adding liquid anydrous ammonia to said reaction mixture to dissolve ammonium chloride therefrom, and thereafter applying an inert gas pressure to the said mixture to filter therefrom the liquid ammonia containing dissolved ammonium chloride.

2. In a purification by extraction of phosphorus-nitrogen compounds obtained by heating phosphorus oxychloride and ammonia to a temperature of at least 100 C. but below 150 C., said compounds being contained in a vessel to remove soluble impurities therefrom by means of liquid anhydrous ammonia, characterized by a cooling efifect in the evaporation of said liquid ammonia,

trogen gas under pressure to the said mixture with the saidliquid anhydrous ammonia, to filter the said liquid ammonia containing dissolved ammonium chloride from the said undissolved condensation products.

4. In the process of extracting ammonium chloride from a mixture with condensation products of phosphorus oxychloride and anhydrous ammonia obtained by heating the said reactants to a' temperature of at least C. but below 0., adding liquid anhydrous ammonia to dissolve ammonium chloride therefrom, and thereafter applying air under pressure to the said mixture with the said liquid anhydrous ammonia to filter from the said mixture the liquid ammonia containing dissolved ammonium chloride. DONALD A. HIGH.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 525,970 Storer et a1 Sept. 11, 1894 2,052,886 Leroy Sept. 1, 1936 2,088,497 Tijmstra July 27, 1937 2,163,085 Cupery June 20, 1939 2,482,756 Ford et a1. Sept. 27, 1949 OTHER REFERENCES Franklin et al.: Amer. Chem. Journal, vol. 20 (1898), pages 820 and 826.

Gladstone: Journ. Chem. Soc., vol. 7 (1869), pages 16-19. 

1. IN THE PROCESS OF EXTRACTING AMMONIUM CHLORIDE FROM A MIXTURE WITH CONDENSATION PRODUCTS OF PHOSPHORUS OXYCHLORIDE AND AMMONIA OBTAINED BY HEATING THE SAID REACTANTS TO A TEMPERATURE OF AT LEAST 100* C. BUT BELOW 150* C., ADDING LIQUID ANYDROUS AMMONIA TO SAID REACTION MIXTURE TO DISSOLVE AMMONIUM CHLORIDE THEREFROM, AND THEREAFTER APPLYING AN INERT GAS PRESSURE TO THE SAID MIXTURE TO FILTER THEREFROM THE LIQUID AMMONIA CONTAINING DISSOLVED AMMONIUM CHLORIDE. 